The identification of the Enterobacteriacae family of bacteria is a common procedure in most medical microbiological laboratories. There are many products available which can be used to accomplish this task, i.e., the API, manufactured by Analytab Products; the R B System manufactured by Corning; the Enterotube manufactured by Roche Diagnostics and the Minitek manufactured by Baltimore Biologic Laboratories (BBL). These systems require a 24 to 48 hour incubation period and essentially are manual in nature. In such systems the unknown organism is introduced into a plurality of media which are later examined for evidence of sustenance of the microorganism by comparing the results of the plurality of tests with a matrix or formula. A determination as to which organism was present initially can be made on a statistical basis.
Since the prior art systems essentially are manual in nature, errors can be made both in determining which media sustain the unknown microorganism and through accidental introduction of other organisms during the handling process which skew the results to make the statistical basis inaccurate. Also, such systems are labor intensive because the many media must be read manually and the addition of indicator chemicals to allow such reading is a time consuming process.
Presently there are existing processes and apparatus for determining the presence, identity and quantity of microorganisms which involve placing the microorganisms into micro quantities of culture media, some of which will sustain specific microorganisms. The media are chemically organized so that the optical characteristics of each changes in a predetermined manner when the media are sustaining specific type or types of microorganisms.
A convenient way to perform these processes is through the use of a card or cassette constructed with a rigid body in the form of a plastic plate which includes viewing wells or chambers which pass through the plate. Each of the wells is connected to a predetermined liquid specimen supply port by means of channels cut in one side of the plate. Each port includes a septum constructed from suitable sealing compound which allows passage of a hollow needle when a liquid specimen is being introduced into the port.
The card is constructed by first forming the plastic plate, inserting the septum and then covering one side of the plate with optically transparent adhesive tape. Chosen biochemical media in liquid form are then placed in the proper wells and freeze dried. The opposite side of the plate is thereafter covered with another layer of optically transparent adhesive tape to form, in effect, a sealed chamber with at least one supply port, a plurality of wells and a piping system therebetween.
To introduce a specimen into the viewing wells, a vacuum is drawn through the specimen and a hypodermic needle inserted through the septum of the filling port so that the air in the sealed chamber is evacuated. The vacuum is removed and atmospheric pressure is used to force the diluted liquid specimen into the card. This causes both the wells and the adjacent branches to be full of liquid containing microorganisms. When no means are provided to prevent it, the microorganisms which are sustained by the media in the viewing wells tend to migrate with the reconstituted media through the branches to other wells. This is undesirable because it can cause erroneous results when the wells are read. This is very important in a matrix type speciation card where multiple organisms may be growing in the same well, each having different locomotion characteristics. Another problem results because some of the metabolic processes of the microbes produce gasses which form bubbles in the viewing wells. Overflow chambers are normally provided adjacent the wells to provide for some bubbles such as those resulting from the filling process and the metabolic bubbles. However, the metabolic bubbles tend to migrate in the heretofore fashioned cards so that they interfere with the optical reading thereof. Also, in a speciation card, it is desirable to change the environmental conditions such as the amount of oxygen in selected wells since some of the matrix tests are best done in an micro aerophilic rather than an aerobic environment.